Emerging health and medical research problems are placing stringent requirements on the ability to characterize labile and high molecular weight organic compounds. In biotechnology, for example, intermediate synthesis products must be identified. Recent ion bombardment desorption models suggest that highest molecular weight compounds would desorb most efficiently through rapid multiple excitations near the molecular attachment site. Resonance ionization spectroscopy has the potential to deliver spatially constrained primary ion bundles on target in the picosecond range. The successive ion arrival time intervals for this source are commensurate with subpicosecond times theoretically predicted for molecular motion and energy transfer to the attachment site. The specific aims of this proposal are: 1) modify a thermal atomization source and ion extraction lens for a primary resonance ionization bombardment source; 2) modify an existing time-of-flight mass spectrometer for higher resolution; 3) evaluate the temporal width of the primary ion pulse; 4) investigate the feasibility of efficient desorption of very high molecular weight species. The potential multiple excitation efficiency and temporal resolution of the proposed source would simultaneously provide the bases for desorption of very high molecules and for an ultra-high resolution time-of-flight mass spectrometer.